The principle of light emission of a light-emitting diode (LED) is different from that of an incandescent light. Besides, the junction temperature of a light-emitting diode (LED) is much lower than the filament temperature of an incandescent light, and therefore an LED is a cold light source. Furthermore, the light-emitting diodes have advantages such as high durability, longer lifetime, lower power consumption, and small size. As a result, the lighting market has high expectation of the light-emitting diodes becoming a new generation of lighting sources to gradually replace the conventional light sources, while the light-emitting diodes are applied to various fields such as traffic lights, back light modules, street lighting, and medical equipment.
FIG. 1A shows a conventional light-emitting device. As shown in FIG. 1A, the conventional light-emitting device 100 comprises a transparent substrate 11, a semiconductor stack 12 on the transparent substrate 11, and an electrode 14 on the semiconductor stack 12, wherein the semiconductor stack 12 comprises a first conductive type semiconductor layer 120, an active layer 122 and a second conductive type semiconductor layer 124 in sequence in a direction from the electrode 14 to the transparent substrate 11.
Besides, the light-emitting device 100 mentioned above is able to further combine with other elements to form a light-emitting apparatus as shown in FIG. 1B. FIG. 1B shows a conventional light-emitting apparatus 200 comprising a submount 15 comprising a circuit 150, a solder 13 on the submount 15, by which the above light-emitting device 100 can be fixed on the submount 15, and by which the substrate 11 of the above light-emitting device 100 is electrically connected to the circuit 150 on the submount 15; and an electrical connection structure 16 for electrically connecting a pad 14 of the light-emitting device 100 to the circuit 150 on the submount 15; wherein the submount 15 can be a lead frame or a large mounting substrate for facilitating the design of the electrical circuit of the light-emitting apparatus 200 and increasing the heat dissipation efficiency.